actioneventdemo.java

《java事件处理指南》一书的代码,好东西

import java.awt.*;
import java.awt.event.*;

//  The ActionEventDemo class, which is a Frame, also serves
//  as an ActionListener.

public class ActionEventDemo extends Frame implements ActionListener {
   Button button;
   MenuBar mb;
   Menu editMenu;
   MenuItem clearMI;
   TextField enterTF, displayTF;

   public ActionEventDemo() {

//  A button is created that is intended to terminate the
//  application when it is pressed.  The button registers
//  an ActionListener that is implemented as an anonymous inner class.
//  When the button is pressed, the actionPerformed() method defined
//  in the anonymous inner class is called and the program terminates.

      button = new Button("Quit");
      button.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent ae) {
            System.exit(0);
         }
      });

//  Two TextFields are created.  The first one, enterTF, is for 
//  the user to type in some text.  When the Return key is pressed,
//  the contents of enterTF will be displayed in the second textfield.
//  The TextFields register the ActionListener implemented
//  by the ActionEventDemo class.  The addActionListener() method is
//  passed the "this" reference meaning the ActionEventDemo object.

      enterTF = new TextField(20);
      enterTF.addActionListener(this);

      displayTF = new TextField(20);
      displayTF.setEditable(false);

//  A MenuBar is created that contains one Menu that contains one
//  MenuItem.  Then the MenuItem is selected, the contents of the
//  TextField at the bottom of the Frame are cleared.

      clearMI = new MenuItem("clear");
      clearMI.addActionListener(this);

      editMenu = new Menu("Edit");
      editMenu.add(clearMI);

      mb = new MenuBar();
      mb.add(editMenu);
      setMenuBar(mb);

      Panel cp = new Panel();
      cp.add(enterTF);
      cp.add(button);
      Panel sp = new Panel();
      sp.add(displayTF);
      add(cp, BorderLayout.CENTER);
      add(sp, BorderLayout.SOUTH);

      setBounds(100, 100, 300, 200);
      setVisible(true);
   }

//  The ActionEventDemo class serves as an ActionListener and must
//  implement the actionPerformed() method.  If the action command
//  associated with the ActionEvent is "clear" that means the button
//  has been pressed and the contents of the displayTF TextField are
//  cleared.  Otherwise, the ActionEvent was generated by the TextField
//  and the content of the displayTF TextField is set to be the text
//  contained by the enterTF TextField.

   public void actionPerformed(ActionEvent ae)
   {
      if ( ae.getActionCommand().equals("clear") ) {
         displayTF.setText("");
      }else {
         displayTF.setText(enterTF.getText());
      }
   }

   public static void main(String args[])
   {
      ActionEventDemo aed = new ActionEventDemo();
   }
}